Epoxy is multi-purpose adhesive. Epoxy resins may react either with themselves or with a wide range of co-reactants. These co-reactants are often called hardeners or curatives.
From the craft class to shipbuilding; from art to science; decoration to industrial applications; adhesives are widely utilized. Before we begin, let us know, what is an adhesive? In simple language, it’s something that holds two or more things together. This might seem like an oversimplification of the actual idea, but it is beneficial to understand the starting point.
Let’s dive a little deeper…
Fundamentally, to understand the discussion a bit further and also that which holds the material together, we come across two vital forces: the adhesive force and the cohesive. It might seem familiar, but it’s ok even if it doesn’t.
The main difference between cohesive and adhesives are: cohesive forces keep like molecules together, whereas adhesive forces act as a binding force between different molecules. These forces play a very important role when you wish to stick something collectively.
It is the adhesive force which makes the glue stick into the wood or even paper. The critical requirements of the adhesive material are as follows:
- Adhesive and structural support/bridging material must be compatible with the material to be combined.
- To get the best result, the bond strength of the substances must be less than breaking point of the substance.
Epoxy resins are at times referred to as polyepoxides. They are a category of reactive prepolymers and polymers that exhibit certain epoxide groups.
Epoxy resins may react either with themselves or with a wide range of co-reactants. These co-reactants are often called hardeners or curatives; also, the cross-linking reaction is better known as curing. The thermosetting polymer can be created by reacting polyepoxides with themselves or with poly-functional hardeners. Thermosetting polymers usually have favorable mechanical properties and high thermal and chemical resistance.
The term epoxy has been widely adopted for many applications beyond fiber reinforced polymer composites. Nowadays, epoxies are commonplace in local hardware shops, and it is used in a number of ways like a binder in countertops or coatings for floors and in various other things.
The myriad uses for epoxy continue to widen, and a large variety of epoxies are increasingly being developed to match the industries and products they are usually used in. Listed below are some things that epoxy resins are used in:
- Solidification of sandy surfaces in oil drilling
- In industrial coatings
- As potting medium
- Reinforcement of fiber with plastics
- General purpose adhesives
- Binding medium in mortars and cement
- In rigid foams
- For non-skid coatings
In the sphere of fiber reinforced polymers, epoxies are used as the resin matrix to hold the fiber in place. It bonds together with most of the reinforcing fibers such as fiberglass, carbon fibers, aramid, and basalt.
Epoxy has become a prominent solution, and one of the revolutionary discoveries as it can stick to wood, metal, glass, stone, and some plastics. Moreover, it has higher heat and chemical resistant than most of the glues in the market. Epoxy can be one of two things. It is either the cured end products of epoxy resins or any of the basic components.
Epoxy resins have been widely used and still continue to be used for coatings, electronic materials, adhesives and matrices for fiber-reinforced composites. This is possible because of certain inherent properties of resins.
Epoxies are known for their high mechanical properties, high adhesion strength, good heat resistance, and high electrical resistance.
The final property of the epoxy resin is affected by a lot of factors like the type of epoxy resin, curing agent, and curing process. So we have to be very careful while using epoxy and choose from a variety of processes in accordance with our needs. As mentioned earlier hardeners are also used in conjunction with epoxy resin.
The properties of cured epoxy resins depend on a lot of factors. They are grouped under the type of epoxy resin, curing agent, and curing process used. The toughness of epoxy resins can be improved by incorporating thermoplastic components, inorganics, carbon fibers, clay, carbon nanotubes, rubber, organic silicon, rigid particles, etc.
Rubber toughening uses a mechanism called “silver streaks – nail anchor” mechanism and “silver lines – shear zone” mechanism. Epoxy’s resistance to impact and a notable improvement to its bending performances is noticed after it has been toughened with rubber. However, there is a noticeable weakening of strength, modulus, and heat resistance.
This is a significant disadvantage, and it is attributed to the epoxy by the lower strength and modulus of rubber. To improve the toughness and yet keep the bending performance, thermoplastic resin modified by rubber can be used.
We should keep in mind that the stiffness and heat resistance is reduced. Nano-particles are known to have large surface activity. This is an advantage as it isn’t difficult to produce a physical and/ or chemical mix with the polymer. In addition to that, it resists micro-crack initiation.
Applications Of Epoxy Compound
- Epoxy has a vast range of applications, including metal coatings, utilization in electronics/electrical parts, high tension electrical insulators, paintbrush production, fiber-reinforced plastic substances, bio-medical systems, aerospace industry and a lot more.
- The resins also help to provide durable, high-gloss outdoor coatings, as well as sealers for concrete floors and other heavy-duty protective coatings used in industrial settings.
- Water-based epoxy paints dry quickly, offering a tough, protective coating. Their reduced volatility and cleaning with water make them useful for factory cast steel, cast iron, and cast aluminium applications, with reduced risk from exposure or flammability than other options available which are based on organic solvents.
- While contrasting with other conventional resins such as thermoset or thermoplastic resins, epoxy resins stand out far above the competition.
They Exhibit The Following Properties:
- Astonishing moisture resistance
- Increase in mechanical and fatigue strength
- Higher resistance to withstand impact
- VOCs are absent
- Longer shelf life
- Low shrinkage during cure
- Higher chemical resistance
- Higher electrical properties
There is a wide range of creative uses of epoxy resins. Epoxy resins are colorless. This provides a strong foundation for a lot of creative ideas. Many DIY crafts and fixtures are made using epoxy resins. Tabletops, wash basins, flooring, lampshades, jewelry, different art fixtures… the list is endless and only limited by imagination.
Epoxy is multi-purpose adhesive, but it is essential to make sure to have proper experience and knowledge before using it. Uncured liquid epoxy resins are mostly classed as an irritant for the eyes and skin. It is also toxic to aquatic organisms. Solid epoxy resins are usually far better in comparison. Exposure to epoxy resins over time can induce allergic reactions. Repeated exposure over an elongated time period can cause sensitization.
Likewise, there are other health hazards involved, hence its necessary to use epoxy with proper care and knowledge. The risk associated with epoxy use is attributed to the hardener component. The epoxy resin alone cannot pose any risk. Especially amine hardeners are usually corrosive in nature, but they might also be categorized as toxic, carcinogenic/ mutagenic.
The article is co-authored by Joy Poddar